Electrical indicating and switching systems



Sept. 30, 1969 M. J. LANGAN ELECTRICAL INDICATING AND SWITCHING SYSTEMS Filed Oct. 24, 1965 FIG. i

FIG. 2

EQUIPMENT FIG.4

PIC-7.3

FIG.5

INVENTOR.

ATTORNEY m G g n O L l n 0 H 0 M FIG.6

United States Patent 3,470,555 ELECTRICAL INDICATING AND SWITCHING SYSTEMS Marion J. Langan, 216 /2 Holmes Ave. NE., Huntsville, Ala. 35801 Filed Oct. 24, 1965, Ser. No. 504,672 Int. Cl. G08b /00, 7/00; H0511 39/00 US. Cl. 340-286 3 Claims ABSTRACT OF DISCLOSURE A switching and indicating circuit which includes an indicating lamp, a relay coil, normally opened relay contacts associated with the relay coil and a source of power and in which all four of these elements are in series and in which switches are included to selectively power to each terminal of the coil to selectively energize or de-energize the coil by closing one of these switches or the other.

coil of the relay and by momentary application of a voltage to the coil and the indicator, by closing a first normally open switch, relay contacts are closed coupling the coil and indicator to a power source through a normally closed second switch, thus sustaining closure of the relayand illumination of the indicator until the second switch is momentarily opened.

Applications for circuitry performing the aforesaid functions are well known and widely employed, for example, in the devices of amusement such as pin ball machines, in industrial control equipment and drive-in restaurants wherev requests for service are made by operating momentary switches. Some such systems employ additional relay contacts other than the one required to sustain relay operation in order/to provide auxiliary functions, but in general it has been found that they do not depart from the basic circuitry and function of having the indicator electrically in parallel with the relay coil as described above. 7

Among the disadvantages of this type of circuit arrangement and operation are unnecessarily complex relay coil construction and the necessity, in many instances, for significant increases in equipment cost to prevent arc suppression as for example by requiring rectifiers or complex impedances across relay coils.

It is an object of this invention to provide an improved electrical relay particularly adapted to series operating circuitry.

It is a further object of this invention to provide switching'and indicating circuitry particularly adapted to perform the functions of initiating, holding and terminating an indicated condition.

In accordance with one aspect of the invention a switching and indicating circuit is constructed of an electromagnetic relay and two terminal indicating device, such as an incandescent lamp and wherein the coil of the relay, the contacts of the relay and the indicating device are all in series. By providing means for selectively energizing the circuit as a whole, two of the three elements and or one of the three elements a wide selection of switching and indicating functions can be achieved. In one form of Patented Sept. 30, 1969 the invention only the coil and indicator are in series. As a particular feature of the invention, the coil and contact points of the relay are adapted to cooperate with like magnitride currents and wherein the relay is a relatively high current operated reed relay and wherein the relay coil is simply wound 'directly on the casing which houses the reed contacts of the relay.

Other objects, features, aspects and advantages of the invention will become apparent from the following description when considered together with the accompanying drawing in which:

FIG. 1 is an electrical schematic diagram of a basic embodiment of the invention;

FIG. 2 is an electrical schematic diagram of a complete switching and indicating system constructed in accordance with the invention;

FIG. 3 is an electrical schematic diagram similar to the basic circuit of FIG. 1 except that there is added auxiliary indicating or control means;

FIG. 4 is an electrical schematic diagram of a switching and indicating circuit wherein the relay contacts are iso lated from the relay coil and indicator lamp indicator energizing circuit;

FIG. 5 is a side view of a reed relay assembly constructed in accordance with the invention; and

FIG. 6 is a side view, partly in section, of a relay-indicator assembly in a housing suitable for mounting the assembly.

Referring now to the drawings, and particularly to FIG. 1, there is shown relay 10, constructed of coil 12 and magnetically associated contacts 14, and incandescent indicator lamp 16. As stated, the particularly significant feature of this circuit is that coil 12 is in series with the indicator lamp instead of being parallel with it, and, another significant feature is that, in addition, all elements, contacts 14, coil 12 and lamp 16 are in series. Further, coil 12, typically required to have a 50 ampere turns capacity, would need only between 50 and 200 turns to meet typical low current indicator bulb-contact point ratings. The wire sizes thus can be fairly large, easy to handle and rugged. These characteristics while, of course, being generally desirable make the relays easy to assemble by hand or by machine. They thus provide the advantage of being not only low power consumption devices, because of low resistance losses, but also low cost devices, a combination not found in presently available relays.

Operation of the circuit is best explained by reference to FIG. 2 which shows additionally energizing circuits 18, 20 and 22, wherein energizing circuit 18 consists of normally open single pole, single throw, switch 24, and power source 26, energizing circuit 20 consists of normally open like type switch 28 and power source 30 and energizing circuit 22, consists of normally closed like type switch 32, and power source 34. Energizing circuit 18 is connected between terminals C and D to provide the momentary on or pulse ofi function, energizing circuit 20, is connected between terminals B and D to provide pulse on functions and energizing circuit 22 is connected between terminals A and D to provide a hold function. Power sources 26, 30 and 34 typically would be identical low voltage sources chosen to provide the proper potential to lamp and may be regarded as a single source 35 with a common connection to switches 24, 28 and 32.

Operation of the circuit is as follows:

(1) Closing switch 24 will operate the indicator lamp 16 but -will cause no current flow through relay coil 12 and consequently have no effect on relay contacts 14;

(2) Closing switch 28 will cause indicator lamp 16 to operate and also will cause current to flow through relay coil 12, thus closing relay contacts '14; and

(3) Presence of a voltage at terminal A, as provided by switch 32 in a closed position, equal to that applied to terminal B will enable removal of a voltage from terminal B without interrupting "the relay or extinguishing the indicator.

Furthermore, with voltage present at terminal A, and removed from terminal B, the indicator may be extinguished and the relay opened by momentary application of voltage to terminal C which is equal to the holding voltage at terminal A. In addition the indicator may be extinguished by momentary removal of the holding voltage at terminal A, or, of course, by disconnection of the ground or return terminal D.

The operation of the circuitry described does require that the operating current of lamp 16 be suflicient to pro* duce closure of relay contacts and that the resistance of relaycoil '1 2 be small in comparison with the resistance of indicator lamp 16. As will become apparent the applicant has discovered that this combination of require ments can be conveniently met with noval and simplified circuit elements. I

It is to be noted that the circuitry of FIGS. 1 and 2 not only accomplishes the same visual indication and memory function as conventional circuitry wherein mo mentary switches initiate sustained indications, but olfers in addition the advantage of permitting indicator turn off with a pulse of the same polarity and magnitude as that which produced indicator turn on. This advantage has heretofore been olfered by equipment including dou ble coil latching relays, which by comparison are significantly more expensive and less reliable.

By making the resistance of relay coil 12 very small with respect to the resistance of indicator 16, the power dissipated in the relay will be a very small percentage of the total power dissipated by the circuit; furthermore,

when it is really needed,

that is when it is needed to "produce a turn onmagnetic force in relay coil 12.

Conveniently, and economically, after the relay is closed the reduced current flow available is all that is needed to hold the relay closed. In other Words the current flow that flows when the bulb is cold provided the neces sary pull inpower,' to operate therelaywhile the current that flows afterward, when the bulb is hot, is sufficient to sustain relayoperation. j

A circuit similar to FIG. I and 2 is shown in FIG. 3, it dilferin'g in that an auxiliary indicator or output circuit is employed. There is added relay 36, havingone or more sets of either normally open or normally closed contacts 38 which are operated when current through indicator 'lamp'16 is initiated or removed. In this way associated equipment may be controlled as, for example, on a fail safe? basis. While, as shown in FIG. 3 an auxiiliary relay as. a whole is added to the circuit, instead, auxiliary contacts may be added to relay 10..

A circuit. similar to theone shown in FIG. 1 is shown in FIG. 4, It differs in that both relay contacts 40 are electrically, isolated from relay, coil 42 of relay 44.. It is an object to this circuitry, as in the case of that shown in FIG. 3, to provide a fail safe type of indicator for interlock purposes, ,or an equipment on indicator whereby failure of the indicator there will result de-energizing of the relay. As shown the associated contacts are used to turn ofi associated equipment and maybe employed toprovide other desired electrical since the relay coil and indicator are in series, the total power must be always less than that which would be consumed by the indicator alone with the same applied voltage.

To further analyse the circuit, consider that the amount of power required to operate an electromagnetic relay is equal to the square of the voltage across the coil divided by the resistance in the coil. Thus in the typically I voltage operated relay, as where Parallel coil-lamp circuitry is used, power consumption must be held to a minimum by the use of a very large number of turns of very fine wire, thus by necessity increasing the complexity and fraility of the circuit. By contrast the circuitry of this invention consumes a minimum of power with a relatively small number of turns of a considerably heavier wire which lends itself to simpler and yet more reliable construction as illustrated in FIG. 5. i

L To sum up the advantages of the'invention as described thus far, it may be stated that: a

(1) the required relay may be appreciably smaller;

(2) the power consumed may be considerably lower;

(3) the relay costs may be considerably lower by virtue of the greatly reduced number of wire turns; and

(4) the reliability may be greater by virtue of reduced breakage associated with heavier wire.

In addition, since the impedance of relay coil 12 is very low, arc suppression may be accomplished by means of'a relatively inexpensive resistor, connected across relay coil 12 without increasing power consumption more than a negligible amount whereas a more expensive diode, or resistance capacitive net-work would be required for a voltage as opposed to a current operated relay as shown.

A still further advantage is that since relay coil 12 is in series with indicator lamp 16, this reduces the input surge current which the latter received, increasing the life of indicator lamp 16. A still further advantage of 'the circuit of the invention is that this initial surge current flow is nevertheless greater than the current that flows after the indicator is lit and becomes hot because the resistance of the filament of an incandescent bulb, as is well known, increases substantially with heat. This increased flow occurs at a time and only at a time,

paths in the event of indicator failure. I

FIG. 5 illustrates a curren operated reed relay con structed in accordance with the invention. Reed contacts 48 and 50are positioned near adjacent ends of support: ing reed members 52 and 54 which in turn are supported in-linc byenlarg'ed end members 56 and 58 of an other-v wise hollow elongated enclosure or tube 60. As shown, the construction of tube 60 is transparent, as of glass or of a clear plastic material, but such is not a material requirement, it only being necessary that there be appropriate electrical insulation of the conductors and minte'rference with the magnetic forces imposed to operate the reed contacts. External terminals 62 and 64 connected to reed members 52 and 54 provide means for electrical connection to the reed contacts.

As a particular feature of the invention, magnetic coil 66 is wound directly on the outer casing of the center portion of enclosure and the ends of the windings are supported by the shoulder provided by enlarged end members 56 and 58. By coordinate adjustment of current requirements, wire size and tube length between shoulders, relay constructiontcan be adjusted for an optimum design to perform in a superior fashion in a wide variety of applications wherein relay contacts are maintained closed upon current flow through the coil of substantially the normal current rating of the contacts.

A third electrical terminal 68'is mounted on enlarged end members 58 for terminating one end of coil 66, the opposite end of coil 66 being terminated directly to terminal 62 of reed member 52. In this manner a series connection is built into the relay between coil 66 and reed contact 48 (and reed contact 50 when coil 66:

is energized).

Resistor 70 is anoptional feature and is connected acrosscoil 66 between terminals '62 and 68 as an arc The operation of the reed relay'shown in FIG. 5 is such that with current flowing through coil 66 the ends of reed members 52 and '54 are caused to be pulled together closing contacts 48 and 50. Typically, reed mem bers 52 and 54 would be constructed of a nickel-iron alloy with plated gold or silver contacts.

FIG. 6 illustrates the actual construction as a circuit sub-assembly of an indicator system as shown schematically in FIG. 1. Reed relay 72, is permanently molded into a surrounding housing 74 which supports indicator assembly 7-5 and electrical leads 76, 78, 80, and 82 to terminals A, B, C, and D, respectively. Coil 84 is wound directly on transparent tubular support 86 of glass or of an insulated plastic material and is hollow between end members 88 and 90, which end members provide support for reed members 92 and 94, before potting and molded in housing 74, which provides further support for reed members 92 and 94.

Incandescent indicator 96 is molded or otherwise affixed to 'be viewable from the exterior of indicator assembly 75 and is connected in series with coil 84 and terminal D. Reed members 92 and 94, supporting contacts 98 and 100, are connected in series between coil 84 and terminal A. Operation of the reed relay of FIG. 4 and indicator assembly of FIG. 5 is as described above with respect to FIGS. 1 and 2. The subassembly as a whole is mounted by conventional means as for example, by a lock ring, not shown, in circular groove 101, on an equipment panel.

Although I have herein shown and described only a few forms of electrical apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described by invention, what I claim is:

1. An electrical indicating system as follows:

(A) an electromagnetic relay having a coil having first and second terminals and at least one set of normally open contacts having first and second terminals associated with and adapted to be closed responsive to the energization of said coil;

(B) indicator means, having first and second terminals, and being adapted to indicate a first condition upon the appliaction of an electrical potential to and between its first and second terminals and to indicate a second condition in the absence of a said electrical potential;

(C) a first series circuit of electrical elements comprising said coil, said set of normally open contacts and said indicator means having a first circuit terminal connecting said second terminal of said indicator means and said first terminal of said coil, a second circuit terminal connecting said second coil terminal and said first terminal of said contacts, a third circuit terminal connected to said second terminal of said contacts and a fourth circuit terminal connected to said first terminal of said indicating means;

(D) a source of said electrical potential comprising a series circuit connected in series between said fourth circuit terminal; and third circuit terminal;

(E) a second series circuit comprising a source of electrical power and a single pole switch connected in series between said fourth circuit terminal and said second circuit terminals; and

(F) coil deenergizing means in circuit with said coil for selectively deenergizing said coil.

2. The indicating system set forth in claim 1 further comprising a third series circuit comprising a source of electrical power and a normally open single pole switch connected between said fourth circuit terminal and said first circuit terminal;

3. The indicating system set forth in claim 2 wherein said coil deenergizing means comprises a normally closed switch in series in said series circuit connected between said fourth circuit terminal and said third circuit terminal.

References Cited UNITED STATES PATENTS 3,128,457 4/1964 Culbertson 340-326 X 2,424,243 7/ 1947 Lowell. 2,706,806 4/1955 Johnson 340332 X THOMAS B. HABECKER, Primary Examiner C. M. MARMELSTEIN, Assistant Examiner US. Cl. X.R. 

